Lenalidomide augments the efficacy of bacillus Calmette-Guerin (BCG) immunotherapy in vivo

Objective: Intravesical bacillus Calmette-Guerin (BCG) is the gold standard for high-grade non-muscle-invasive bladder cancer (NMIBC); however, some patients do not respond to initial therapy while others relapse and/or progress. Therefore, combination strategies that can enhance the efficacy and sustainability of BCG are needed. Herein, we explore the efficacy of lenalidomide, a thalidomide derivative with immunomodulatory effects, in combination with BCG, both in vitro and in vivo. Materials and methods: We explored the outcomes of lenalidomide in combination with BCG in vivo using the MBT-2 cell line implanted in C3H immunocompetent mice. Apoptosis, cell proliferation, and microvessel density were measured by immunohistochemistry. In vitro, we performed Western blotting for cell cycle and apoptosis regulatory proteins and a chromatin condensation assay to evaluate TNF-α and FasL in combination with lenalidomide. Results: In the mouse model, combination therapy with BCG and lenalidomide resulted in a statistically significant decrease in tumor size compared with the control group. IHC demonstrated a nonsignificant increase in apoptosis in the combination condition and no effect on cellular proliferation. Microvessel density was decreased in all treated conditions. In vitro, caspase-3 activation and chromatin condensation studies demonstrated increased cell death in the combinations of lenalidomide and TNF-α. Conclusions: The immunomodulatory molecule lenalidomide augments the response to BCG in an in vivo mouse model. This provides the rationale for studying the combination in patients with high grade NMIBC.